We make our own.
The process is a little long, but worth the effort - and you CAN do other things in the meantime!
You should buy the best quality UNsalted butter possible.
Place as many cakes, sticks or bars of it, as you want, in a heavy-bottomed stainless-steel pan, (about 3 or 4 will do) with 500ml of water.
As gently as is possible, melt all the butter, until it is a clear liquid floating on the water.
Do NOT stir, do NOT allow the mixture to boil. Avoid, if you can, any bubbling, although a little bit once the butter is melted, is ok.
Turn off the heat, and allow the butter to cool and solidify. Once cold and solid, try to make some room in the fridge and store it over night.
In the morning, take an apple corer and make a hole right at the edge, where the butter meets the pan. Pierce the butter to make another hole, just about opposite (this is to let air in, as you pour the water out....).
Give the pan a gentle swill, and then pour the water away.
You will see that the water is milky/cloudy.
Those are the milk solids being separated from the butter oil.
Through the hole you have made, pour another 500ml of water.
Repeat the above process two more times, until the water you pour off is completely clear. (That's 3 times in all)
The last times you do this, put the pan, with the solid cake of butter in it, on the stove, and heat on a low heat. No water this time though! (4th time of heating).
Bring the butter up to a simmer, and let it popple on the stove. Skim off any surface froth that might form and stay there, and simmer it for around 15 minutes.
Pour into clean, sterilised glass jars. Close immediately. Allow to cool on the side, then store in the fridge.
Will keep for at least 2 years.
This ghee has an extremely high burning point, (unlike butter) so it's very good for gently frying or sautéeing all manner of foods.
Butter begins to burn very quickly, because of the milk solids. That's what burns when butter starts going brown in your pan.
And yes - you CAN use it for cake-making.
I sterilise my jars by washing them carefully, then pouring boiling water in them (one-third full) and putting them in a microwave for 1 minute.
Remove them with oven gloves, pour off the water, and stand on a plate. Make sure they are completely dry when you pour the butter in though. Use a clean kitchen paper towel.
Sterilise the lids by placing in a dish, and pouring boiling water on them and leaving them for a minute. Remove, shake off, dry the inside with a clean kitchen paper towel.
I know it's a lengthy process, but it works well, is worth it, and the ghee is extremely nutritious. Make enough and it will last you a good, long time.